:Potassium hexafluoronickelate(IV)

{{Chembox

| ImageFile = K2NiF6.svg

| ImageSize =

| IUPACName = potassium hexafluoronickelate(IV)

| OtherNames =

|Section1={{Chembox Identifiers

| CASNo = 17218-47-2

| CASNo_Ref = {{cascite|correct|scifinder}}

| PubChem =

| EINECS = 625-130-0

| ChemSpiderID = 21241633

| SMILES = [K+].[K+].F[Ni-2](F)(F)(F)(F)F

| InChI = InChI=1S/6FH.2K.Ni/h6*1H;;;/q;;;;;;2*+1;+4/p-6

}}

|Section2={{Chembox Properties

| Formula = K₂NiF₆

| MolarMass = 250.880

| Appearance =

| Density =

| MeltingPt =

| BoilingPt =

| Solubility =

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|Section3={{Chembox Hazards

| Hazards_ref = {{cite web|title = Potassium Hexafluoronickelate(IV)|url =https://www.americanelements.com/potassium-hexafluoronickelate-iv-17218-47-2|publisher = American Elements|accessdate = December 19, 2018}}

| ExternalSDS = [https://www.americanelements.com/printpdf/potassium-hexafluoronickelate-iv-17218-47-2/sds External SDS]

| GHSPictograms = {{GHS06}}{{GHS07}}{{GHS08}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|302|312|317|331|350}}

| PPhrases = {{P-phrases|201|261|280|304+340|405|501}}

| MainHazards =

| FlashPt =

| AutoignitionPt =

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Potassium hexafluoronickelate(IV) is an inorganic compound with the chemical formula {{chem|K|2|NiF|6}}. It can be produced through the reaction of potassium fluoride, nickel dichloride, and fluorine.

It reacts violently with water, releasing oxygen. It dissolves in anhydrous hydrogen fluoride to produce a light-red solution. Potassium hexafluoronickelate(IV) decomposes at 350 °C, forming potassium hexafluoronickelate(III), nickel(II) fluoride, and fluorine:{{in lang|zh-hans}}{{cite book|title=《无机化学丛书》第九卷：锰分族、铁系、铂系|pages=P333|author=张青莲|isbn=7-03-002238-6|location=北京|publisher=科学出版社}}{{better source needed|date=December 2013}}{{Cite journal |last=Stein |first=Lawrence |last2=Neil |first2=John M. |last3=Alms |first3=Gregory R. |date=November 1969 |title=Properties of potassium hexafluoronickelates(III) and -(IV). Absorption spectra of nickel(III) and -(IV) in hydrogen fluoride solutions |url=https://pubs.acs.org/doi/abs/10.1021/ic50081a045 |journal=Inorganic Chemistry |language=en |volume=8 |issue=11 |pages=2472–2476 |doi=10.1021/ic50081a045 |issn=0020-1669|url-access=subscription }}

:$\backslash rm\; \backslash \; 3\; K\_2NiF\_6\; \backslash xrightarrow\{\backslash Delta\}\; 2\; K\_3NiF\_6\; +\; NiF\_2\; +\; 2\; F\_2$

Image:Mg2FeH6 from X-ray.jpg

Potassium hexafluoronickelate is a strong oxidant. It can turn chlorine pentafluoride and bromine pentafluoride into {{chem|ClF|6|+}} and {{chem|BrF|6|+}}, respectively:{{cite journal|doi=10.1021/ic001024|title=Novel Synthesis of ClF₆⁺ and BrF₆⁺ Salts|year=2001|last1=Schroer|first1=Thorsten|last2=Christe|first2=Karl O.|journal=Inorganic Chemistry|volume=40|issue=10|pages=2415–9|pmid=11327921}}

:$\backslash rm\; \backslash \; K\_2NiF\_6\; +\; 5\; AsF\_5\; +\; XF\_5\; \backslash xrightarrow\{aHF\}\; XF\_6AsF\_6\; +\; Ni(AsF\_6)\_2\; +\; 2KAsF\_6$

:( X = Cl or Br , -60 °C , aHF = anhydrous hydrogen fluoride).

Potassium hexafluoronickelate decomposes at high temperatures to release fluorine gas; like terbium(IV) fluoride, the emitted fluorine is primarily monatomic rather than the typical diatomic.{{cite journal |last1=Rau |first1=J. V. |last2=Chilingarov |first2=N. S. |last3=Leskiv |first3=M. S. |last4=Sukhoverkhov |first4=V. F. |last5=Rossi Albertini |first5=V. |last6=Sidorov |first6=L. N. |title=Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine |journal=Le Journal de Physique IV |date=August 2001 |volume=11 |issue=PR3 |pages=Pr3–109–Pr3-113 |doi=10.1051/jp4:2001314}}

It adopts the structure seen for K₂PtCl₆ and Mg₂FeH₆.Taylor, J. C. "A comparison of profile decomposition and Rietveld methods for structurtal refinement with powder diffraction data" Zeitschrift für Kristallographie 1987, volume 181, p151-160.